The role of cavity size in the evolution of clutch size in tree swallows

  • Published source details Stewart L. & Robertson R. (1999) The role of cavity size in the evolution of clutch size in tree swallows. The Auk, 116, 553-556.


This study is summarised as evidence for the following.

Action Category

Provide artificial nesting sites for songbirds

Action Link
Bird Conservation
  1. Provide artificial nesting sites for songbirds

    A replicated trial in summer 1992 in a wetland in Ontario, Canada (Stewart & Robertson 1999), found that tree swallow Tachycineta bicolor clutches were significantly smaller in small nest boxes than in large (average of 5.8 eggs/clutch for 11 small boxes and 6.5 eggs/clutch for 12 large) and fewer eggs hatched, although this difference was not significant (72% of eggs hatching in small boxes vs. 84% in large). Once brood sizes were standardised by transferring chicks between nests, there were no differences in the timing of reproduction, chick mass or size or fledging rates (91% for small boxes vs. 97% for large), although nestling flight feathers were shorter after 15 days in small boxes, possibly due to overcrowding. All nest boxes were the same when installed, but after swallows began nesting, small boxes had an insert installed, which reduced the basal area from 178 cm2 to 75 cm2.


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